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Biomedical subjects

K J Chen

Publications and source records attributed to K J Chen.

At least 19 recordsLinked to original sources
PubMed2005

The initial ocular following responses elicited by apparent-motion stimuli: reversal by inter-stimulus intervals.

Transient apparent-motion stimuli, consisting of single 1/4-wavelength steps applied to square-wave gratings lacking the fundamental ("missing fundamental stimulus") and to sinusoidal gratings, were used to elicit ocular following responses (OFRs) in humans. As previously reported [Sheliga, B. M., Chen, K. J., FitzGibbon, E. J., & Miles, F. A. (2005). Initial ocular following in humans: a response to first-order motion energy. Vision Research, in press], the earliest OFRs were strongly dependent on the motion of the major Fourier component, consistent with early spatio-temporal filtering prior to motion detection, as in the well-known energy model of motion analysis. Introducing inter-stimulus intervals (ISIs) of 10-200 ms, during which the screen was gray with the same mean luminance, reversed the initial direction of the OFR, the peak reversed responses (with ISIs of 20-40 ms) being substantially greater than the non-reversed responses (with an ISI of 0 ms). When the mean luminance was reduced to scotopic levels, reversals now occurred only with ISIs > or=60 ms and the peak reversed responses (with ISIs of 60-100 ms) were substantially smaller than the non-reversed responses (with an ISI of 0 ms). These findings are consistent with the idea that initial OFRs are mediated by first-order motion-energy-sensing mechanisms that receive a visual input whose temporal impulse response function is strongly biphasic in photopic conditions and almost monophasic in scotopic conditions.

Contrast Sensitivity↗
PubMed2005

Initial ocular following in humans: a response to first-order motion energy.

Visual motion is sensed by low-level (energy-based) and high-level (feature-based) mechanisms. Ocular following responses (OFR) were elicited in humans by applying horizontal motion to vertical square-wave gratings lacking the fundamental ("missing fundamental stimulus"). Motion consisted of successive 1/4-wavelength steps, so the features and 4n+1 harmonics (where n=integer) shifted forwards, whereas the 4n-1 harmonics--including the strongest Fourier component (the 3rd harmonic)--shifted backwards (spatial aliasing). Initial OFR, recorded with the electromagnetic search coil technique, were always in the direction of the 3rd harmonic, e.g., leftward steps resulted in rightward OFR. Thus, the earliest OFR were strongly dependent on the motion of the major Fourier component, consistent with early spatio-temporal filtering prior to motion detection, as in the well-known energy model of motion analysis.

Contrast Sensitivity↗
PubMed2005

Short-latency disparity vergence in humans: evidence for early spatial filtering.

Our study was concerned with the disparity detectors underlying the initial disparity vergence responses (DVRs) that are elicited at ultrashort latencies by binocular disparities applied to large images. DVRs were elicited in humans by applying horizontal disparity to vertical square-wave gratings lacking the fundamental (termed here, the "missing fundamental"). In the frequency domain, a pure square wave is composed of odd harmonics--first, third, fifth, seventh, etc.--such that the third, fifth, seventh, etc., have amplitudes that are one-third, one-fifth, one-seventh, etc., that of the first, and the missing fundamental lacks the first harmonic. The patterns seen by the two eyes have a phase difference of one-quarter wavelength, so the disparity of the features and 4n + 1 harmonics (where n = integer) has one sign (crossed or uncrossed), whereas the 4n - 1 harmonics--including the strongest Fourier component (the third harmonic)--has the opposite sign (uncrossed or crossed): spatial aliasing. The earliest DVRs, recorded with the search-coil technique, had minimum latencies of 70 to 80 ms and were generally in the direction of the third harmonic, that is, uncrossed disparities resulted in convergent eye movements. In other experiments on the DVRs, one eye saw a missing fundamental and the other saw a pure sine wave with the contrast and wavelength of the third harmonic but differing in phase by one-quarter wavelength. This resulted in short-latency vergence in accordance with matching of the third harmonic. These data all indicate the importance of the Fourier components, consistent with early spatial filtering prior to binocular matching.

Fourier Analysis↗
PubMed2005

Initial ocular following in humans depends critically on the fourier components of the motion stimulus.

Visual motion is sensed by low-level (energy-based) and high-level (feature-based) mechanisms. Our interest is in the motion detectors underlying the initial ocular following responses (OFR) that are elicited at ultrashort latencies by sudden motions of large images. OFR were elicited in humans by applying horizontal motion to vertical square-wave gratings lacking the fundamental. In the frequency domain, a pure square wave is composed of the odd harmonics--first, third, fifth, seventh, etc.--such that the third, fifth, seventh, etc., have amplitudes that are one-third, one-fifth, one-seventh, etc., that of the first, and the missing fundamental stimulus lacks the first harmonic. Motion consisted of successive quarter-wavelength steps, so the features and 4n+1 harmonics (where n = integer) shifted forward, whereas the 4n-1 harmonics--including the strongest Fourier component (the third harmonic)--shifted backward (spatial aliasing). Thus, the net Fourier energy and the non-Fourier features moved in opposite directions. Initial OFR, recorded with the search coil technique, had minimum latencies of 60 to 70 ms and were always in the direction of the third harmonic, for example, leftward steps resulted in rightward OFR. Thus, the earliest OFR were strongly dependent on the motion of the major Fourier component, consistent with mediation by oriented spatiotemporal visual filters as in the well-known energy model of motion detection. Introducing interstimulus intervals of 10 to 100 ms (during which the screen was uniform gray) reversed the initial direction of tracking, consistent with extensive neurophysiological and psychophysical data suggesting that the visual input to the motion detectors has a biphasic temporal impulse response.

Fourier Analysis↗
PubMed2004

A panel study on the effects of a Chinese medicinal suppository, Vigconic VI-28, on insulin-like growth factor 1 and homocysteine in healthy men.

Changes in serum homocysteine (Hcy), often related to stroke and vascular dementia, are negatively correlated with changes in serum insulin-like growth factor 1 (IGF-1) and growth hormone (GH) replacement decreases Hcy levels in men with GH deficiency. Very little information on the effects of Chinese medicines on GH and Hcy is available in the literature published in English. In this study, the effects of a Chinese medicine suppository, Vigconic VI-28 (VI-28), consisting of concentrated extracts of a composite mixture of herbal materials, on serum IGF-1 and Hcy were studied. In vivo observations after treatment with Chinese medicines have often indicated changes in biochemical profiles of measurable parameters related to those changes in endocrine secretions. Thirty six healthy males (age 47-66) were under observation over a 16-week schedule after using VI-28 suppository from 0 to 12 weeks. Blood specimens were taken monthly (except at the end of week 8) for analysis of Hcy and IGF-1 levels. Compared with week 0, IGF-1 levels (192.5 +/- 66.4 ng/ml) were significantly elevated at week 4 (211.7 +/- 80.5, p < 0.05) and week 12 (226.6 +/- 95.2 ng/ml, p = 0.01). No significant changes were observed for Hcy for the whole cohort from week 0 to week 16. When the cohort was divided into 2 groups using a Hcy level of 13.0 micro mol/l as the cut-off, a significant (p < 0.05) difference in IGF-1 was observed between the 2 groups at week 12 only. The mean IGF-1 of 14 subjects with higher Hcy levels was lower than that of the 22 subjects with lower Hcy. We believe that VI-28 may exert a regulatory effect on the relationship between Hcy and IGF-1, at least in subjects with relatively low levels of Hcy. In addition, we also observed an apparent association of hyperhomocysteinemia (Hcy> or =13.0 micromol/l) with decreased IGF-1.

Aged↗
PubMed2004

Risk factors for peptic ulcer disease in renal transplant patients--11 years of experience from a single center.

BACKGROUND: Peptic ulcer disease is a common complication among renal transplant recipients and causes significant morbidity and mortality. METHODS: From 1990 through 2000, 465 renal transplant patients were followed-up in our institute. Most patients received corticosteroids and cyclosporine-based immunosuppressive regimen. About one third (n = 156) of them received mycophenolate mofetil. Patients with endoscopy-proved peptic ulcer disease were identified by reviewing medical records. Possible risk factors were analyzed by univariate analysis and multiple logistic regression analysis. RESULTS: Among 465 kidney transplant patients, there were 181 (38.9%) who suffered at least 1 episode of peptic ulcer disease. The most frequent types of peptic ulcer disease were gastritis, gastric ulcer, duodenal ulcer, esophagitis, duodenitis and esophageal ulcer. By multivariate analysis, the use of methylprednisolone pulse therapy (odds ratio = 3.954, 95% confidence interval = 3.154-18.312, p = 0.03) and history of pre-transplant peptic ulcer disease (odds ratio = 7.599, 95% CI = 1.211-12.905, p < 0.0001) were independent risk factors for posttransplant peptic ulcer disease. CONCLUSIONS: Our findings demonstrated that renal transplant patients who undergo methylprednisolone pulse therapy for acute rejection or who have a history of pre-transplant peptic ulcer disease carry a high risk for the development of peptic ulcer disease and deserve intensive antiulcer treatment.

Adolescent↗
PubMed2002

Modeling head tracking of visual targets.

Control of the head involves somatosensory, vestibular, and visual feedback. The dynamics of these three feedback systems must be identified in order to gain a greater understanding of the head control system. We have completed one step in the development of a head control model by identifying the dynamics of the visual feedback system. A mathematical model of human head tracking of visual targets in the horizontal plane was fit to experimental data from seven subjects performing a visual head tracking task. The model incorporates components based on the underlying physiology of the head control system. Using optimization methods, we were able to identify neural processing delay, visual control gain, and neck viscosity parameters in each experimental subject.

Algorithms↗
PubMed2001

Sesquiterpenes from the Formosan stolonifer Tubipora musica.

Eight new sesquiterpenes, tubipolides A-G (1-7) and tubiporone (8) (novel carbon skeleton), and a known sesquiterpene, spirotubipolide, have been isolated from the Formosan stolonifer Tubipora musica. The structures of compounds 1-8 were determined by 1D and 2D NMR spectral analysis.

Animals↗
PubMed2001

Central areolar choroidal and retinal pigment epithelial dystrophy: a family report.

Central areolar choroidal and retinal pigment epithelial dystrophy (CACD) is a rare hereditary macular disease characterized by a bilateral, symmetric, and well-circumscribed solitary area in the macula with choroidal and retinal pigment epithelial atrophy. We report a family of CACD confirmed by both clinical presentation and hereditary pattern. Three members of the family were examined. They had noticed gradual visual deterioration with poor color discrimination since the fourth to fifth decades. All of them showed a bilaterally symmetric bull's-eye pattern of macular dystrophy with a sharp border of underlying large or middle choroidal vessels, which was unassociated with any surrounding lesions. Fluorescein angiography revealed a transmission window defect due to retinal pigment epithelial atrophy with remaining choriocapillaris intermingled with a hypofluorescent area of choriocapillaris atrophy. Electroretinography revealed a mild reduction in the photopic amplitude, while the scotopic response was normal. A normal electro-oculography was also noted. The family history indicated autosomal dominant inheritance. The loss of visual acuity was caused by progressive atrophy of both the retinal pigment epithelium and the choriocapillaris. It is important to detect CACD in the early stages, because this diagnosis can exert a considerable influence on a patient's subsequent life.

Aged↗
PubMed2001

Ocular ischemic syndrome.

BACKGROUND: The purpose of this study was to investigate the clinical features and management of ocular ischemic syndrome (OIS) and factors influencing its development. METHODS: Ten patients (12 eyes) with OIS underwent detailed medical and ocular histories, complete ophthalmic evaluation including fluorescein angiography, internal carotid artery evaluation by duplex ultrasonography, and management. The following outcome measures were considered: visual acuity, anterior segment neovascularization, lens status, retinal and choroidal changes, and carotid artery stenosis or occlusion. RESULTS: The mean age of the patients was 63 +/- 8 years. Presenting visual symptoms included gradual (82.5%) or sudden (17.5%) onset of vision loss. At initial visit, eyes with OIS had visual acuity less than or equal to counting fingers in 50%, iris neovascularization in 58%, and neovascular glaucoma in 42%. Initially associated systemic diseases in these patients included arterial hypertension (60%), diabetes mellitus (40%), coronary artery disease (20%), previous stroke (30%) and hemodialysis (10%). Complete occlusion or severe occlusion (70-99%) of the internal carotid artery was seen in 75% on the side of OIS. Panretinal photocoagulation did not prevent OIS from progressing but vitreous hemorrhage and rubeosis iris regressed. Carotid endarterectomy had some benefit in stabilizing or improving vision in patients with OIS. CONCLUSION: OIS has a poor visual prognosis. It is imperative that the clinician be aware of the signs and symptoms of carotid disease in order to facilitate prompt diagnosis and appropriate referral, because OIS may be the presenting sign of serious ischemic cerebrovascular and ischemic heart disease.

Adult↗
PubMed2001

[Relationship between coronary angiography and syndrome differentiation type of TCM].

OBJECTIVE: To understand the relationship between the coronary Angiography (CA) reflected degree of coronary artery lesion and the TCM Syndrome Differentiation-type (TCM-SDT). METHODS: Patients TCM-SDT were differentiated adopting the standard of Syndrome Differentiation for coronary artery diseases revised in 1990, and the comparison of TCM-SDT with the findings in CA was carried out. RESULTS: CA examination showed that 29 patients (39.73%) were of one-artery lesion, 9 patients (12.33%) two-artery lesion and 35 patients (47.95%) three-artery lesion; the stenosis degree of them were: 54 arteries were mild stenosis, 38 moderate stenosis and 31 severe stenosis; 29 arteries were completely occluded, the sum total of affected artery was 152 (69.41%), and the other 67 arteries (30.59%) had no lesion. TCM-SDT showed that all the 73 patients had secondary Excess Syndrome, among them 73 patients (100%) with blood stasis Syndrome, 39 patients (53.4%) with Phlegm-Turbid Syndrome, 16 (21.0%) with Qi-stagnation Syndrome and 7 (9.6%) with Cold condensation Syndrome. 63 patients (86.3%) with obvious primary Deficiency Syndrome, among them, 57 (78.1%) were Qi-Deficiency, 18 (24.7%) Yang-Deficiency, 28 (38.4%) Yin-Deficiency and 5 (6.8%) Yang collapse. All patients had blood stasis of various degrees, manifesting on tongue proper prominently. In the 80.8% patients who had angina pectoris, 74.0% had their mouth, lips and gum dark red, dark purple or light dark in color. The comparison between TCM-SDT and Blood-Stasis score revealed that patients of Cold condensation-blood stasis Syndrome and Yang collapse-blood stasis Syndrome were serious. Patients of Qi stagnation-blood stasis Syndrome and Yin Deficiency-blood stasis Syndrome were mild cases, while patients of Phlegm Turbid-blood stasis Syndrome and Qi Deficiency-blood stasis Syndrome were moderate severity cases. The number of affected artery in Cold condensation patients was the most, and in Yin-Deficiency patients was the least. The coronary artery stenosis degree in patients of Qi-stagnation and Yin-Deficiency were milder than in those of Yang-collapse and Yang-Deficiency patients. CONCLUSION: The more the number of arterial lesion, the severer the degree of stenosis and the higher the blood stasis score, then the more serious the degree of stasis.

Adult↗
PubMed2001

[Effect of xiongshao capsule on vascular remodeling in porcine coronary balloon injury model].

OBJECTIVE: To study the effect of Xiongshao Capsule (XS) on vascular remodeling in porcine coronary balloon injury model. METHODS: Restenosis model was established by oversized balloon injury at mid-region of the left anterior descending coronary artery. The effect of drugs on late lumen loss and vascular remodeling was evaluated with quantitative histological method by combining results from histopathological analysis and coronary arteriography. RESULTS: Vascular remodeling explained (59 +/- 20)% of late lumen loss. All drugs significantly reduced late lumen loss 4 weeks after balloon injury (P < 0.05 or 0.01). Both low-dose and high-dose XS markedly reduced late lumen loss resulting from vascular remodeling, as compared with the control group (P < 0.05 and P < 0.01 respectively). CONCLUSION: Vascular remodeling played an important role in late lumen stenosis after balloon injury of coronary artery. XS could significantly inhibit pathological vascular remodeling after balloon injury, thus reduce late lumen loss and prevent restenosis.

Angioplasty, Balloon, Coronary↗
PubMed2001

[Effect of combination of Chinese herbal drugs on clinical bioavailability of ferulic acid in serum].

OBJECTIVE: To observe the effect of combination of Chinese herbal drugs on bioavailability of Ligusticum walichii (LW) derived ferulic acid (FA) in serum. METHODS: Healthy volunteers were given LW decoction (1 g/kg), LW combined with Paeonia veitchii (PV, 1:1) decoction (2 g/kg) and Coronary Heart No. 2 (CH-II, 3 g/kg, containing LW 0.5 g/kg) once respectively. The serum FA concentration-time (c-t) curve was performed by HPLC using the method established by the authors, and the area under that curve (AUC) was calculated and compared. RESULTS: The FA c-t curve in the three groups was double peak curve. As compared with the AUC in subjects who were administered LW decoction, the AUC in those taken LW + PV decoction was lower [(15734.88 +/- 7737.97) ng/(min.ml) vs (5717.92 +/- 6124.63) ng/(min.ml)], P < 0.05), while that in those taken CH-II was relatively higher [(8072.00 +/- 4424.31) ng/(min.ml), P > 0.05)]. CONCLUSION: Combination of LW and PV could significantly lower the bioavailability of FA, but when LW was added in CH-II, the FA bioavailability was not affected.

Adolescent↗
PubMed2001

[Protective effect of yixinkang capsule containing serum on oxygen stress damaged mitochondrial membrane potential in guinea-pig myocytes].

OBJECTIVE: To explore the protective effect and mechanism of Yixinkang (H303) capsule, a composite preparation of Chinese herbal medicine for antagonizing myocardial ischemia, containing serum on oxygen stress damaged mitochondrial membrane potential (MMP) in guinea-pig myocytes. METHODS: Myocyte damage was induced by incubating myocytes with hydroxy free radical (Fe2+/H2O2) generating system for 30-60 mins, then H303-containing serum was added in to observe the protective effect. MMP was detected by laser scanning confocal microscopy. RESULTS: After oxygen stress, the cytochrome oxidase (CCO) activity and MMP in mitochondria significantly decreased. These changes could be significantly lessened by H303-containing serum, demonstrated as obviously increase of CCO activity and myocyte survival rate. H303-containing serum also showed a significant protective effect on membrane potential of myocytes. CONCLUSION: Oxygen stress could cause decrease of MMP in myocytes and H303-containing serum could protect it to maintain the membrane stability of mitochondria.

Animals↗
PubMed2001

[The protective effects of yi-xin-kang capsule on the structure and function of rat myocardial mitochondria].

OBJECT: To observe the injury induced by Isoproterenol (ISO) on the structure and function of rat myocardial mitochondria and the protective effects of Yi-Xin-Kang Capsule (H303). METHOD: After injection of ISO, rat myocardial mitochondria were isolated. The activities of phospholipidase A2(PLA2) and Ca(2+)-ATPase, the content of phospholipids (PL) and high-energy phosphates, membrane lipid fluidity (LFU) and respiration function were determined respectively. RESULT: ISO induced severe injury to myocardial mitochondria. The activity of PLA2 was significantly activated. The intensity of LFU, the activity of Ca(2+)-ATPase, respiration function of mitochondria and the contents of PL and high-energy phosphates of myocardium tissue were significantly decreased. Oral administration of H303 significantly decreased the activity of PLA2. The contents of PL and LFU, the activity of Ca(2+)-ATPase were significantly increased. The respiration function of mitochondria was protected by accelerating III state respiration rate, improving ADP/O ratio and recovering the depressed respiration control rate. CONCLUSION: H303 possessed protective effect on structural and functional injury of mitochondria induced by ISO.

Animals↗
PubMed2000

Nitration and hydroxylation of aromatic amino acid and guanine by the air pollutant peroxyacetyl nitrate.

Peroxyacetyl nitrate (PAN) is a common gaseous photochemical compound in polluted air and cigarette smog. The toxicity of PAN has been found to depend on three pathways: (1) its oxidizing property that mimics peroxide or peroxynitrite; (2) its nitrating and hydroxylating properties similar to peroxynitrite; and (3) its acetylating property like acetic anhydride. The present investigations were intended to focus on the reactions of PAN with aromatic amino acids and guanine. When PAN interacted with tyrosine and guanine the major products were 3-nitrotyrosine, 3, 5-dinitrotyrosine, 8-hydroxyguanine and 8-nitroguanine. These compounds have been used as indicators for the presence of peroxynitrite in previous studies. When PAN interacted with phenylalanine, the products were 3-nitrotyrosine, 4-nitrophenylalanine, p-tyrosine, o-tyrosine and m-tyrosine. 5-Hydroxytryptophan is produced from the reaction of PAN with tryptophan. Furthermore, the formation of nitrated tyrosines was also found in the PAN-treated HL-60 cells. A high yield of dityrosine was formed when PAN and peroxynitrite were reacted with tyrosine, probably through free radical oxidation. We also found that peroxynitrite and PAN are similar in their oxidizing activity. From these findings, we suggest that peroxynitrite may be considered as the reactive intermediate of PAN.

Air Pollutants↗
PubMed2000

Effect of lipanthyl on mRNA expression of endothelin-1 and nitric-oxide synthase in atherosclerotic vessel wall in rabbits.

AIM: To study the mechanism of regression of atherosclerosis (AS) by lipanthyl. METHODS: Experimental atherosclerotic rabbits created by damaging the abdominal aortic endothelium and feeding with high fat diet for 8 wk were then treated with lipanthyl 15 mg.kg-1.d-1 for 16 wk. Expression of endothelin (ET)-1 mRNA and nitric oxide synthase (NOS) mRNA in atherosclerotic vessel wall was measured by in situ hybridization and reverse transcription polymerase chain reaction (RT-PCR), respectively. RESULTS: After lipanthyl administration for 16 wk, ET-1 mRNA expression was reduced, and integral optical density (IOD) and area of hybridization granule were observed to be (49,113 +/- 16,868) and (2448 +/- 621) micron 2 in lipanthyl group and (65,188 +/- 10,113) and (3028 +/- 352) micron 2 in atherosclerotic group, respectively. Regarding inducible NOS mRNA expression, IOD and area were decreased by 25.5% and 53.3%, respectively, whereas endothelial NOS mRNA expression was increased. CONCLUSION: Restoration of the disturbed ET-1 mRNA/NOS mRNA balance by lipanthyl might be one of its mechanisms leading to regression of atherosclerosis.

Animals↗